Weird Electrical Bug

I had a simular proiblem on my 81. It had a bad rotor. I had a good 70-79 rotor. I got the R/S magnets and put one on the 70-79 rotor. It ran great with the reg/rec unplugged, stalled as soon as I plugged it in.
With a bunch of experementing I could get it too run with the reg/rec plugged in but I had to reverse the wires at the brushes. The only thing I can think of was for some reason the rotor polarity effects the TCI pickups. The magnet I tried both ways, polarity didn't matter. I put in a good 80 up rotor, and things run great.
I know this isn't exactly your problem but you might try reversing the polarity of your rotor just to see if it runs.
Leo
 
I bought a new reg/rec hoping that was the problem, but it runs the same so it was not the reg/rec. The rotor is recent, about 6 months old with a rare earth magnet stuck to it, just to see I pulled the new rotor off of my other bike and it ran the same with that one too.

I am at a loss and I am not willing to put any more money into it until I am sure that what I buy will fix the problem. I would rewire the whole bike if I thought it would do any good but I can find nothing wrong with the existing wiring.
 
Its a SWAG, but it sounds to me that you've got AC voltage/current flowing in your ignition circuit where you don't want it. That would explain why it runs raggedy when the alternator is connected.
Sooo,...
1. Look for a wiring short of the white alternator wires to frame. When the AC goes negative that would probably induce current through the plug(s) and cause a misfire.
2. Instead of pulling apart the entire plug to the alternator, try removing one wire at a time to isolate the culprit.
3. Do you have access to an oscilloscope...?

Dave
 
Have you measured between the white wires of the stator to earth?
Disconnected from your wiring loom, there should be no resistance.
I had a simmular problem coused by a short circuit in the stator
 
I have measured the resistance on the white wires and they are good.

I do have access to an oscilloscope. What would you like me to check?
 
Playing with an osciliscope may be fun and tell you a lot of things but all you need are the ohms checks from wire to wire and wires to the body if off the bike, to ground on the bike.
Some years spec .9 ohms, some spec .46 ohms. As long as they are all the same it is probably ok. Infinity to ground or body. Be sure to unhook the yellow wire to the safety relay, if not you will be measuring the ohms of the relay not ohms to ground.
Leo
 
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I have a similar issue with my '83. The charging system quit working. Took it to a bike shop and they said it needed a regulator and possibly a rotor. I put in a new regulator and it didn't fix anything. But the rotor had only 1.8 ohms between the faces so I bought a new rotor and installed it. Then the bike wouldn't fire at all. Upon inspection it seems the folks in Bejing put the magnet in the wrong place. Well, when I used the tool to tap the rotor loose, my hammer slipped and tapped the face of the stator. Can't return it....
So I've been experimenting with moving the magnet to coincide to where it was on my old rotor. I now have the bike running with the new rotor but it won't go above 2500 RPM. Battery voltage at that RPM is 12.39 VDC. What a quandary. Bike runs great with old, non-charging, rotor.
 
No resistance between white wires and ground.

It is a G schematic.

I swapped the polarity on the brushes and it runs awesome but it does not charge.

I have another 1980 that runs great witha new rotor and swapped that rotor in and it made no difference.
 
scratch my last post. My dad swapped the wrong wires. Swapping the right wires to reverse the polarity gives me a fantastic running bike that charges!

What makes it so I would need to swap the polarity?
 
I've got the same problem on my '83. It wasn't charging. Took it to a bike shop and they said it was a regulator or rotor. I replaced the regulator with no effect. Then replaced the rotor and it wouldn't even fire. Turns out the rotor builders in Peking didn't get the magnet in the right spot. I replaced the magnet (Radio Shack) and it would fire and pop and barely run to 2500 rpm. At 12.39 VDC on the battery. But if I unhook the regulator plug, it runs like a champ. So we both have the same problem. With no solution.
 
Charlie said:
upb2010:
Which wires need to be swapped? The brush wires????
Click to expand...

My magnet is in the right spot. No clue why the rotor switched polarity though. I swapped the brush wires, the green and brown ones. Try it, it might work for you too
 
Charlie when you replaced the magnet did you just lay it on the old and epoxy it?
Seems I read the magnet is to far away from the pickup and adding one on top of the existing magnet fixes that?
 
No, I dug the magnet out and moved it so it coincided with the magnet on the original rotor, then drilled a shallow hole and JB welded a Radio Shack rare earth magnet in the correct position. Now the bike starts and gets up to about 2500 RPM where it sputters and coughs like mad. Unhookiing the regulator lets the bike run fine. I'm out of ideas, As an aside, the timing mark on the new rotor is not in the same place as the mark on the old rotor. It's about 4 or 5 degrees different. Removed the LH spark plug and TDC of that piston agrees with the old rotor timing mark. I placed the magnet on the new rotor to coincide with where it is on the old rotor.
I'm glad I still have the original ,non charging, rotor. At least the bike starts and runs fine with it installed. Just won't charge.:banghead:
 
Charlie, get your old rotor rewound. Call Gary at Custom Rewinds, 800-798-7282. Last I checked the rewinds were $125. It won't cost you to call.
Leo
 

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